Transdigm Group Incorporated (TDG) is 21.67% of Mark Massey's AltaRock Partners portfolio as of September 30, 2026, according to the 13F-HR filed with the SEC on November 13, 2026: 843K shares worth about $913M, the 3rd largest of 8 stock positions. Mark Massey trimmed the share count by 4% in 2026 Q3.
What did the 2026 Q3 filing report for TDG?
As of September 30, 2026, from the 13F-HR filed November 13, 2026.
| Value | |
|---|---|
| Portfolio weight | 21.67% |
| Shares | 843K |
| Reported value | $913M |
| Rank in portfolio | 3rd of 8 |
| Largest holding | MSFT at 32.15% |
| Top three holdings | 82.35% of the book |
| Change this quarter | -4% shares |
How concentrated is Mark Massey in TDG?
TDG at 21.67% is 1.7 times the average stock position in the Mark Massey portfolio, which is 13%. The largest holding is MSFT at 32.15%. The three largest stocks together are 82.35% of the reported book. A quarter earlier TDG was 27.51% of the book.
Where does TDG sit in the Mark Massey portfolio?
TDG ranks 3rd of 8 stock positions in the Mark Massey portfolio at 21.67%, above the fund's average stock position of 13%. The TDG cut was the 4th largest of the quarter's 7 position changes by percent change to portfolio. Across the 2026 Q3 portfolio, Mark Massey reported 8 stock positions, with no position opened or closed. The total portfolio value is about $4.21B, down 1% from the prior quarter.
How long has Mark Massey held TDG?
Mark Massey first reported TDG in the quarter ended December 31, 2014. The weight peaked at 32.29% in 2015 Q4. Last quarter the fund cut the position by 4%. Every reported trade is on the Mark Massey TDG trade history page.
Did other funds buy or sell TDG in 2026 Q3?
Among the other tracked funds that had filed for 2026 Q3 as of November 13, 2026, 2 hold TDG. Of those, one opened it this quarter. The largest buyers of TDG this quarter were Vulcan Value Partners and Chuck Akre. Every tracked holder of TDG is on the TDG ownership page.
FAQ
What share of the Mark Massey portfolio is TDG?
TDG is 21.67% of the Mark Massey portfolio as of 2026 Q3, the 3rd largest of 8 stock positions.
What is the TDG stake of Mark Massey worth?
Mark Massey holds 843K shares of TDG, worth about $913M at September 30, 2026 prices, 21.67% of the reported portfolio.
What are the largest holdings of Mark Massey?
The largest stock positions of Mark Massey as of 2026 Q3 are MSFT (32.15%), AMZN (28.53%) and TDG (21.67%), together 82.35% of the book.
Did Mark Massey's AltaRock Partners change its TDG position in 2026 Q3?
Mark Massey trimmed the share count by 4% in 2026 Q3.